As a type of ophthalmic diagnostic equipment, there are tomographic image capturing devices that utilize optical interference of so-called OCT (Optical Coherence Tomography) to capture tomographic images of ocular fundi. Such tomographic image capturing devices can capture tomographic images of ocular fundi at high sensitivity through irradiating the ocular fundi with broadband and low coherent light and causing the reflected light from the ocular fundi to interfere with reference light. When the horizontal direction, vertical direction and depth of an ocular fundus are represented by x-direction, y-direction and z-direction, respectively, such a tomographic image capturing device can acquire tomographic pictures (B-scan pictures) in the xz-directions. In ordinary image capturing of OCT, the tomographic images are captured, for example, at a rate of 40 images per second and a set of 100 or more tomographic pictures of a retina can be acquired by one-time testing (image capturing at a part of the retina).
In general, when capturing tomographic images, adjustment of an image capturing condition, such as positioning of an image capturing site and reference mirror, focus adjustment, and determination of a dispersion compensation glass, may be performed before the image capturing so that optimum tomographic pictures of an ocular fundus are obtained. As illustrated in FIG. 7, when raster scan is performed for image capturing of a three-dimensional tomographic structure, there is a method in which adjustment of the image capturing condition before the image capturing is performed while observing tomographic pictures obtained by sequentially scanning only in a high-speed axis direction (x-direction) at the center of a scanning field angle that is two-dimensionally set, and thereafter the original scanning field angle as a whole is raster-scanned at the time of actually capturing tomographic images. In such a method, the tomographic pictures obtained at the time of adjustment of the image capturing condition are approximately fixed and the form variation of the image capturing site is less likely to occur in the tomographic pictures. Therefore, adjustment can easily be performed for the appearance position of the image capturing site in the tomographic pictures and for the image capturing condition, such as focus adjustment, which may be advantageous.
On the other hand, when the raster scan area is wide, when the object is an eye of high myopia, when images of the peripheral area of a retina are captured, when images of an area of optic papilla are captured, or in similar cases, the curvature of captured tomographic pictures is large, so that the appearance positions of the image capturing site in the tomographic pictures differ in accordance with the scanning position. Therefore, an appropriate focus position and reference mirror position cannot be determined even if the image capturing condition is optimized by performing adjustment of the image capturing condition on the basis of the tomographic pictures obtained only by scanning the center position of raster scan because the form of the measurement object cannot be perceived except the center position of raster scan. As a result, in the tomographic pictures obtained by scanning other parts than the center position of raster scan, defocus and/or replication of the tomographic structure of the image capturing site may possibly occur. In addition, if the appearance position of image capturing site is unnecessarily set below to prevent such replication, the image contrast may deteriorate.